JP2001-180908A published by the Japanese Patent Office in 2001 discloses a fuel reforming system comprising a reforming reactor which generates hydrogen-rich reformate gas from a hydrocarbon fuel, water and air, a shift reactor and preferential oxidation reactor which remove carbon monoxide from the reformate gas, and a burner which supplies heat used for warmup to the reactors when the system starts up.
In this prior art technology, when the system starts up, fuel is first burnt in excess air, and the temperature of the reforming reactor is raised by passing the burnt gas into the reforming reactor. When the reforming reactor has warmed up, the combustion in the burner is changed over to excess fuel conditions to start the fuel reforming reaction in the reforming reactor, and the reformate gas produced is supplied together with air and burnt in the shift reactor and preferential oxidation reactor to raise the temperature of these reactors.